Why Nepal quake was so damaging

The magnitude-7.8 earthquake that devastated much of Nepal on 25 April did not relieve all of the geological stress in the region — making another big quake probable.

Credit: Narendra Shrestha/EPA/Corbis

A team led by Jean-Philippe Avouac at the University of Cambridge, UK, used seismic data and satellite radar to show that a 140-kilometre stretch of a major Himalayan geological fault shifted during the disaster. This transferred stress into neighbouring areas of the fault, which may now be more prone to rupturing in a future quake.

In a separate paper, Yuji Yagi and Ryo Okuwaki of the University of Tsukuba, Japan, found that the earthquake rupture raced eastward from its point of origin. The greatest movement of the fault occurred about 50 kilometres east of the quake's epicentre — close to Kathmandu.

This discovery helps to explain why the shaking was so destructive to the city, according to a third paper by another team led by Avouac. Although much of the ground in the region shook only moderately, the seismic energy was amplified across the Kathmandu basin in ways that caused tall buildings, including temples, to sway and collapse (pictured is what remains of Kathmandu's Bhimsen Tower, known as Dharahara).

Nature Geosci. http://doi.org/6p7 (2015); Geophys. Res. Lett. http://doi.org/6ns (2015); Science http://doi.org/6p6 (2015)